Effect of 3.39 micron radiation on the frequency characteristics of a helium-neon laser at 0.63 micron

In a theoretical and experimental study of a helium-neon ring laser operating on the basis of two simultaneous transitions, 3s$sub 2$--2p$sub 4$ (lambda=0.63 $mu$) and 3s$sub 2$--3p$sub 4$ (lambda=3.39 $mu$), it is found that the coupling of these transitions leads to a situation in which the IR generation leads to a significant change in the frequency characteristics of the visible light. In the case of unidirectional lasing at lambda=3.39 $mu$, with a finite frequency difference between the frequency of this radiation and the center of the amplification line, an additional frequency difference arises between the oppositely directed waves with lambda=0.63 $mu$. This difference, which reaches several tens of kilohertz, is found as a function of the laser properties. (AIP)